The objective of this study is to define the phenotype and genetic basis of previously undescribed types of familial diabetes insipidus (FDI). All consenting members of kindreds in which novel types of FDI appear to be segregating will be addmitted to the CRC for a series of tests to determine the presence, absence, cause, natural history, clinical concomitants and mode of interitance of the FDI. This information will serve to improve the accuracy of phenotyping and clarify the pathogenesis of this and other types of FDI.